Drop support for gtk+ < 2.24
GTK_IS_COMBO_BOX is deprecated, use gtk_combo_box_get_has_entry
GTK_DIALOG_MODAL is also available in gtk+2
Fix glib deprecations

Based on evince commit by Carlos Garcia Campos <carlosgc@gnome.org>
Url: https://git.gnome.org/browse/evince/commit/?id=bf90f90e0af99bbfdd20e6d21fd228c05cffae51
Url: https://git.gnome.org/browse/evince/commit/?id=76151be92239ed5f491cb26c87a2328b670e9f64
Bump GLIB version